JP2010098885A - Method and apparatus for driving step motor, and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for driving a step motor, capable of reliably removing backlash by simple control, and to provide a camera. <P>SOLUTION: In an apparatus capable of driving an object to be driven while using a step motor 50 as a drive source, a microcontroller 60 sets a first driving frequency for generating a torque capable of removing the backlash of a lens barrel without generating a torque capable of driving the lens barrel, drives the step motor 50 at the number of predetermines pulses based on the first driving frequency, and then, sets a second driving frequency generating a torque to drive the lens barrel. Then, the microcontroller starts to drive the step motor 50 based on the second driving frequency, and starts to detect the driving amount of the stepper motor 50. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a stepping motor driving technique, and more particularly to a stepping motor driving method, a driving apparatus, and a camera capable of obtaining precise feeding accuracy even when backlash occurs.

  The step motor is widely used as a driving device for speed or position control in digital equipment such as a camera, OA equipment such as a copying machine, FAX, or FA equipment such as a machine tool. In order to drive such a step motor, it is necessary to subdivide and control the step angle.

By the way, when driving a lens using a step motor, backlash inevitably exists in the lens driving mechanism. However, since backlash occurs due to this backlash, for example, in Patent Document 1 below, as a means for removing the backlash of the lens drive mechanism, the reduction gear train is reduced by lowering the energization start voltage to the motor. A technique for taking backlash is described.
JP-A-63-172241

  However, in the above-described apparatus, the lens may move to the lens with the first applied voltage due to variations in the load, or the motor may stop at the second applied voltage. In the case of using a DC brush motor, the relationship between the voltage and the motor speed changes due to the change of the brush contact resistance with time, making it difficult to obtain the desired control. In addition, a circuit and IC for changing the voltage are required, leading to an increase in cost.

  Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to drive a step motor that can reliably remove backlash by simple control in a lens driving mechanism using a step motor. It is to provide a method and a driving device and a camera.

  That is, the present invention relates to a step motor driving method in an apparatus capable of driving a driven body using a step motor as a driving source, and the back of the driven body is generated without generating a torque capable of driving the driven body. A first drive frequency that generates a torque capable of removing rush is set, and after the step motor is driven a predetermined number of pulses based on the first drive frequency, a second torque that can drive the driven body is generated. The driving frequency is set, the driving of the step motor is started based on the second driving frequency, and the detection of the driving amount of the step motor is started.

  The present invention also relates to a step motor driving method in an apparatus capable of driving a driven body using a step motor as a driving source, and the back of the driven body is generated without generating a torque capable of driving the driven body. After selecting a first table storing a driving frequency that generates torque capable of removing rush, and driving the step motor for a predetermined number of pulses based on the first table, torque that can drive the driven body is generated. The second table storing the driving frequency is selected, and the driving of the step motor is started based on the second table, and the detection of the driving amount of the step motor is started.

  The present invention comprises a step motor, a driven body driven by the step motor, a drive means for driving the step motor, and a control means for supplying a drive pulse to the drive means. Sets a first driving frequency that generates a torque that can remove backlash of the driven body without generating a torque that can be driven by the driven body, and the step based on the first driving frequency. After driving the motor for a predetermined number of pulses, a second drive frequency that generates torque that can drive the driven body is set, and the step motor is started based on the second drive frequency and the step motor is driven. The detection of the driving amount is started.

  The present invention further comprises a step motor, a driven body driven by the step motor, a drive means for driving the step motor, and a control means for supplying a drive pulse to the drive means. The means selects a first table storing a first driving frequency that generates a torque capable of removing backlash of the driven body without generating a torque capable of driving the driven body, and based on the table After driving the step motor for a predetermined number of pulses, a second table storing a second drive frequency that generates torque that can be driven by the driven body is selected, and the driving of the step motor is started based on this table. Detection of the driving amount of the step motor is started.

  The present invention includes a step motor, a driven body driven by the step motor, a driving means for driving the step motor, a control means for supplying a driving pulse to the driving means, and the driven body can be driven. A first table storing a driving frequency that generates a torque that can remove backlash of the driven body without generating a torque, and a second table storing a driving frequency that generates a torque capable of driving the driven body. A storage means having a table, and the control means selects a first table of the storage means, drives the step motor based on the first table for a predetermined number of pulses, and then The second table is selected, and the step motor drive is started based on the second table and the detection of the drive amount of the step motor is started. The features.

  The present invention is characterized in that the step motor driving device is applied for driving a photographing lens.

  ADVANTAGE OF THE INVENTION According to this invention, in the lens drive mechanism using a step motor, the drive method and drive device of a step motor which can remove backlash reliably by simple control, and a camera can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus to which the present invention is applied.

  The imaging apparatus 10 includes a zoom lens group 11 including a variable power lens group 11 and a focus lens group 12, a diaphragm mechanism 13 for controlling exposure, a CCD image sensor 14 for converting a subject image into an electrical signal, and the CCD image sensor 14. An imaging circuit 15 that converts a signal into a digital signal, an AE processing unit 18, an AF processing unit 19, an image processing circuit 20, and a nonvolatile memory that are connected to the signal bus 100 and perform various processing on the digitized imaging signal 21, a built-in memory 22, a compression / decompression unit 23, a memory card 24, and an LCD driver 25.

  Further, the imaging apparatus outputs a system controller 30 for comprehensively controlling each unit, an input unit 31 including various operation switches, a TG circuit 32 for controlling the CCD imaging device 14, a CCD driver 33, an alarm, and the like. Speaker 34, power supply unit 35, LCD 37 for displaying operation state and mode state, zoom control unit 41 for driving control of lens, focus control unit 42, aperture control unit 43 for controlling aperture 13, step Motors 49, 50, 51 and motor drivers 45, 46, 47 for driving the step motors 49, 50, 51 are provided.

  In the imaging apparatus 10, the system controller 30 performs all the control, and in particular, is responsible for a series of processes related to exposure control, signal readout by drive control of the CCD imaging device 14, and image processing. Yes.

  Next, the operation of the imaging apparatus 10 will be described.

  The input unit 31 is provided with various operation switches such as a zoom lever, a release SW, and a power switch. When the photographer performs an operation to change the angle of view with the zoom lever, the system controller 30 instructs the zoom control unit 41 to drive the step motor 49 via the motor driver 45 and move the variable magnification lens group 11. Is output.

  Subsequently, when the photographer operates the release SW and pushes it in one step, AE and AF operations are performed. In the AE operation, the image signal from the imaging circuit 15 is taken into the AE processing unit 18. The AE processing unit 18 calculates an AE evaluation value obtained by integrating image signals in a predetermined area and transmits the value to the system controller 30.

  When the system controller 30 compares the AE evaluation value with the internal reference value and determines, for example, that the brightness of the subject is low, the system controller 30 increases the amplification factor of the imaging circuit 15 via the TG circuit 32 or the aperture control unit. 43 is driven via a motor driver 47 to instruct an operation such as opening / closing of the diaphragm 13. In this way, appropriate exposure control is executed.

  Next, an AF operation is performed. The image signal from the imaging circuit 15 is input to the AF processing unit 19, and the AF processing unit 19 extracts a high-frequency component from the image signal by filter processing. Then, an AF evaluation value obtained by integrating the high frequency components or a contrast value is calculated, and the value is transmitted to the system controller 30. The system controller 30 controls the focus controller 42 to drive the step motor 50 via the motor driver 46 so that the AF evaluation value is maximized. In this way, focus control is executed.

  When the release SW is pushed in two steps, a normal shooting operation is started.

  When the photographing operation is started, the image of the subject is formed on the image sensor 14 through the variable power lens group 11, the focus lens group 12 and the diaphragm 13. The imaging signal generated by the imaging device 14 is input to the imaging circuit 15, subjected to processing such as CDS (correlated double sampling) and signal amplification, and then converted to a digital signal and output to the signal bus 100. .

  Connected to the signal bus 100 are an AE processing unit 18, an AF processing unit 19, an image processing circuit 20, a nonvolatile memory 21, a built-in memory 22, a compression / decompression unit 23, a memory card 24, an LCD driver 25, and the like.

  The image data from the imaging circuit 15 is once buffered in the built-in memory 22 and then subjected to processing such as Y / C and color matrix in the image processing circuit 20. Then, the image is compressed in the compression / decompression unit 23 and then stored in the memory card 24. On the other hand, image data from the imaging circuit 15 is input to the LCD driver 25 as a video signal and displayed on the LCD 37 as a through image.

  When the photographer performs an image reproduction operation, the image data stored in the memory card 24 is read, and the compression / decompression unit 23 performs decompression processing. Thereafter, the image is converted into an image of a required size by the image processing circuit 20, input to the LCD driver 25, and displayed on the LCD 37.

  The nonvolatile memory 21 stores various programs or set values for performing the above-described processes.

  FIG. 2 is a diagram showing a lens driving mechanism and its control system in the focus lens group 12 of FIG.

  Although not shown in FIG. 2, the focus lens group 12 is mounted in the lens barrel portion 53. A step motor 50 and a gear unit 56 that transmits the driving force of the step motor 50 are provided at predetermined end portions of the lens barrel portion 53. The rotation shaft of the step motor 50 is connected to the input shaft of the gear unit 56. The cam frame 55 is slidably provided in the circumferential direction of the lens barrel portion 53, and a gear 55 a that meshes with a pinion gear 56 a that is an output gear of the gear unit 56 is provided on the inner surface of the cam frame 55. Partly formed.

  The cam frame 55 is formed with cam grooves 57 obliquely along the circumferential surface thereof. On the other hand, a cam pin 58 that is movable in the axial direction is formed at a predetermined position of the focus lens group described above.

  The step motor 50 is driven by a drive signal output from the system controller 30 via the microcontroller 60 in the focus control unit 42 and the motor driver 46. The microcontroller 60 includes a flash ROM (Flash ROM) 61 in which control parameters such as a program and a drive frequency of the step motor 50 are stored.

  Now, when the step motor 50 is driven by an instruction from the system controller 30, the gear 55a and the gear unit 56 mesh with each other, whereby the cam frame 55 rotates in a predetermined direction along the circumferential surface of the lens barrel 53. . Then, the position of the cam pin 58 relatively moves along the cam groove 57. That is, since the cam pin 58 moves only in the axial direction, the focus lens group 12 coupled to the cam pin 58 moves in the axial direction in accordance with the position of the cam pin 58, and a focusing operation is performed. .

  Next, with reference to the flowchart in FIG. 3 and the timing chart in FIG. 4, a method for driving the step motor 50 of the imaging apparatus 10 in the first embodiment will be described.

  This control operation is mainly performed by the system controller 30.

When this sequence is started, first, a signal of a predetermined high frequency pulse is output from the system controller 30 to the motor driver 46 via the microcontroller 60 in step S1. Then, in accordance with this signal, the motor driver 46 starts driving the step motor 50 from time t ₁ . Next, in step S2, it is determined whether or not the number of pulses from the start of driving of the step motor 50 has reached a predetermined amount.

In the case of normal step motor drive, as shown in the timing chart of FIG. 4A, the step motor drive frequency is gradually increased from the start of driving (time t ₁ ), that is, the motor speed. Is getting faster. However, when the focus lens group is moved in the direction opposite to the current movement direction, backlash due to backlash occurs between the gears in the gear unit 56 and between the gear unit 56 and the gear 55a of the cam frame 55. When the stepping motor 50 is accelerated in this state, backlash is eliminated, and the stepping out occurs when the load of the focus lens group is applied to the stepping motor 50.

In contrast, in the present embodiment, as shown in the timing chart of FIG. 4B, only the period T1 (time t _{1 to} t ₃ ) during which a predetermined amount of pulses is obtained from the start of driving of the motor is high. And it is driven at a frequency of a constant period. This period T1 is the time used for backlash removal. That is, when the motor starts driving, the frequency is high and the driving torque is small. Therefore, the focus lens group 12 with a large load is not driven, and the gear 55 a between the gear unit 56 and the cam frame 55 is not driven. The engagement portion is in contact with the backlash generated in the engagement portion. This eliminates backlash.

  FIG. 5 is a diagram showing the relationship between the drive frequency of the step motor 50 and the drive time of the motor.

  FIG. 5 shows that when there is a lens load, that is, when the lens is actually driven, the lens is driven at about 1000 pps. On the other hand, it is shown that the lens is driven at approximately 3000 pps for removing the backlash before the lens is loaded, that is, before the lens is driven. In this case, it can be seen that the motor is driven at a frequency three times as high as the frequency with the lens load for backlash removal. Further, at pps between F1 in the figure, driving is possible only when there is no lens load.

When the backlash is removed in this way, the process proceeds to step S3, and the acceleration driving of the step motor 50 is started based on the load driving table (program) of the flash ROM 61 of the microcontroller 60 in the focus control unit 42. (Time t ₃ ). At the same time, in step S4, counting of drive pulses is started by a counter (not shown) in the system controller 30. Thereby, the measurement of the driving amount of the lens frame is started.

  Next, in step S5, the frequency corresponding to the number of drive pulses is read from the load drive table, and the drive frequency of the step motor 50 is changed. In step S6, it is determined whether or not the number of pulses for driving the lens frame has reached a predetermined value, that is, whether or not the lens frame has moved to the target position. If the number of pulses has not reached the predetermined value, the process proceeds to step S5, and the above-described operation is repeated until it is determined that the lens frame has moved to the target position.

  Although not shown in the timing chart of FIG. 4, when the lens frame has moved to the target position, that is, when the number of pulses has reached a predetermined value, the driving of the step motor 50 is stopped in step S7, The sequence ends.

  As described above, according to the first embodiment, before the lens is actually driven, the step motor is driven for backlash removal at a frequency higher than that of the lens drive. Backlash can be removed.

(Modification)
In the first embodiment described above, the driving pulse frequency and the number of driving pulses for removing backlash have been described as fixed parameters. However, the present invention is not limited to this, and a plurality of driving pulses may be provided.

  For example, if the photographic lens is a zoom lens, backlash may vary depending on the focal length, so prepare multiple parameters and select the appropriate parameter according to the focal length. Also good. Alternatively, a plurality of parameters may be prepared according to the taking-out position of the photographing lens, and the parameters may be selected according to the driving position.

  Thus, by preparing a plurality of parameters, it is possible to shorten the time required for backlash removal.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  In the first embodiment described above, the drive frequency of the step motor for backlash removal is made constant, but in the second embodiment, the drive frequency of the step motor for backlash removal is also accelerated.

  In the second embodiment described below, the configuration and basic operation of the image pickup apparatus 10 are the same as those of the image pickup apparatus 10 according to the first embodiment shown in FIGS. Therefore, for these configurations and operations, the same reference numerals are given to the same parts, and illustration and description thereof will be omitted, and only different operations will be described.

  FIG. 6 is a flowchart for explaining a method of driving the step motor 50 of the imaging apparatus 10 according to the second embodiment of the present invention.

  Hereinafter, with reference to the flowchart in FIG. 6 and the timing chart in FIG. 4, a method for driving the step motor 50 of the imaging apparatus 10 in the first embodiment will be described.

  This control operation is mainly performed by the system controller 30.

When this sequence is started, a signal of a predetermined high frequency pulse is first output to the motor driver 46 from the system controller 30 via the microcontroller 60 in step S11. Then, in accordance with this signal, the motor driver 46 starts driving the step motor 50 from time t ₁ . Next, in step S12, the frequency corresponding to the number of drive pulses is read from the backlash removal table data in the flash ROM, and the drive frequency of the step motor 50 is changed. That is, as shown in the timing chart of FIG. 4 (c), the frequency of the drive pulses from the time t ₁ will be changed gradually to a higher frequency side.

  Then, in the following step S13, it is determined whether or not the number of pulses for removing backlash has reached a predetermined amount. If the number of pulses has not reached the predetermined amount, the process proceeds to step S12, and the above-described operation is repeated until the number of pulses reaches the predetermined amount.

If the number of backlash removal pulses reaches a predetermined amount (time t ₂ ), the process proceeds to step S14. In step S14, acceleration driving of the step motor 50 is started based on the load driving table data of the flash ROM 61 of the microcontroller 60 in the focus control unit 42 (time t ₂ ). At the same time, in step S15, counting of drive pulses is started by a counter (not shown) in the system controller 30. Thereby, the measurement of the driving amount of the lens frame is started.

  Next, in step S16, a frequency corresponding to the number of drive pulses is read from the load drive table data, and the drive frequency of the step motor 50 is changed. In step S17, it is determined whether or not the number of pulses for driving the lens frame has reached a predetermined value, that is, whether or not the lens frame has moved to the target position. If the number of pulses has not reached the predetermined value, the process proceeds to step S16, and the above-described operation is repeated until it is determined that the lens frame has moved to the target position.

  Although not shown in the timing chart of FIG. 4, if the lens frame has moved to the target position, that is, if the number of pulses has reached a predetermined value, the driving of the step motor 50 is stopped in step S18, The sequence ends.

  As described above, according to the second embodiment, by driving the step motor based on the backlash removal table data, the backlash can be removed earlier than the first embodiment described above. .

(Modification)
In the second embodiment described above, the table data storing drive pulses for removing backlash and the number of drive pulses are described as fixed parameters. However, the present invention is not limited to this, and a plurality of drive pulses may be provided.

  For example, when the photographing lens is a zoom lens, a plurality of parameters may be prepared according to the focal length, and the corresponding parameter may be selected according to the focal length. Alternatively, a plurality of parameters may be prepared according to the taking-out position of the photographing lens, and the parameters may be selected according to the driving position.

  Thus, by preparing a plurality of parameters, it is possible to further reduce the time required for backlash removal.

  In the above-described embodiment, the frequency of the drive pulse for removing the backlash is made higher (the pulse width is made narrower) than the drive pulse for driving the lens. However, the present invention is not limited to this.

  For example, the backlash removal pulse and the lens driving start pulse may be the same. However, in this case, the pulse for removing the backlash is not counted as the driving amount.

  As mentioned above, although embodiment of this invention was described, in the range which does not deviate from the summary of this invention other than embodiment mentioned above, this invention can be variously modified.

  Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be obtained as an invention.

It is a block diagram which shows the structure of the imaging device to which this invention is applied. It is the figure which showed the lens drive mechanism and its control system in the focus lens group 12 of FIG. 3 is a flowchart for explaining a method of driving a step motor 50 of the imaging apparatus 10 according to the first embodiment. 6 is a timing chart for explaining a method of driving the step motor 50 of the imaging apparatus 10 according to the first embodiment. It is a figure showing the relationship between the drive frequency of step motor 50, and the drive time of this motor. It is a flowchart for demonstrating the drive method of the step motor 50 of the imaging device 10 in the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Imaging device, 11 ... Variable magnification lens group, 12 ... Focus lens group, 13 ... Aperture mechanism, 14 ... CCD image sensor, 15 ... Imaging circuit, 18 ... AE processing part, 19 ... AF processing part, 20 ... Image processing Circuit: 21 ... Non-volatile memory, 22: Built-in memory, 23 ... Compression / decompression unit, 24 ... Memory card, 25 ... LCD driver, 30 ... System controller, 31 ... Input unit, 32 ... TG circuit, 33 ... CCD driver, 34 ... Speaker, 35 ... Power supply unit, 37 ... LCD, 41 ... Zoom control unit, 42 ... Focus control unit, 43 ... Aperture control unit, 45, 46, 47 ... Motor driver, 49, 50, 51 ... Step motor, 53 ... Lens barrel section, 55 ... cam frame, 55a ... gear, 56 ... gear unit, 56a ... pinion gear, 578 ... cam groove, 58 ... cam pin, 60 ... micro controller .

Claims (11)

A step motor driving method in an apparatus capable of driving a driven body using a step motor as a driving source,
Setting a first driving frequency that generates a torque capable of removing backlash of the driven body without generating a torque that can be driven by the driven body;
After driving the stepping motor for a predetermined number of pulses based on the first driving frequency, a second driving frequency that generates torque that can drive the driven body is set.
A step motor driving method characterized by starting driving the step motor based on the second driving frequency and starting detecting the driving amount of the step motor.   2. The step motor driving method according to claim 1, wherein driving of the step motor starting with the second driving frequency as a reference is either acceleration driving or constant speed driving. 3. A step motor driving method in an apparatus capable of driving a driven body using a step motor as a driving source,
Selecting a first table storing a driving frequency that generates a torque capable of removing backlash of the driven body without generating a torque capable of driving the driven body;
After driving the stepping motor for a predetermined number of pulses based on the first table, select a second table that stores a driving frequency that generates torque that the driven body can drive,
A step motor driving method characterized by starting driving of the step motor based on the second table and starting detecting the driving amount of the step motor.   4. The stepping motor driving method according to claim 3, wherein the driving of the stepping motor stored in the second table is either acceleration driving or constant speed driving. A step motor,
A driven body driven by the step motor;
Driving means for driving the step motor;
Control means for supplying drive pulses to the drive means;
Comprising
The control means sets a first drive frequency that generates a torque capable of removing backlash of the driven body without generating a torque capable of driving the driven body, and based on the first drive frequency Then, after driving the step motor for a predetermined number of pulses, a second drive frequency that generates torque that can drive the driven body is set, and driving of the step motor is started based on the second drive frequency. Detection of the drive amount of the step motor is started. A drive device for a step motor.   6. The stepping motor driving device according to claim 5, wherein the control means drives the stepping motor that starts driving based on the second driving frequency at either acceleration or constant speed. A step motor,
A driven body driven by the step motor;
Driving means for driving the step motor;
Control means for supplying drive pulses to the drive means;
Comprising
The control means selects a first table storing a first driving frequency that generates a torque that can remove backlash of the driven body without generating a torque that can drive the driven body, and this table. After driving the step motor based on the predetermined number of pulses, the second table storing the second driving frequency that generates torque that can be driven by the driven body is selected, and the driving of the step motor is started based on this table. And detecting the drive amount of the step motor.   The step motor driving apparatus according to claim 7, wherein the control means drives the step motor, which starts driving based on the second driving frequency, at either acceleration or constant speed. A step motor,
A driven body driven by the step motor;
Driving means for driving the step motor;
Control means for supplying drive pulses to the drive means;
A first table storing a driving frequency that generates torque that can remove backlash of the driven body without generating torque that can be driven by the driven body, and driving that generates torque that can drive the driven body Storage means having a second table storing the frequency;
Comprising
The control means selects the first table of the storage means, drives the step motor based on the first table for a predetermined number of pulses, selects the second table, and stores the second table in the second table. And a step motor driving device that starts driving the step motor and starts detecting the driving amount of the step motor.   The step motor driving apparatus according to claim 9, wherein the control means drives the step motor, which starts driving based on the second drive frequency, at either acceleration or constant speed.   11. A camera, wherein the step motor driving device according to claim 5 is used for driving a photographing lens.

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